.'.i 



lii I '! 




DEPARTMENT OF COMMERCE 

BUREAU OF FISHERIES 

HUGH M. SMITH, Commissioner 



SOME PLANTS OF IMPORTANCE IN POND- 
FISH CULTURE 

By EMMELINE MOORE, Ph. D. 



APPENDIX IV TO THE REPORT OF THE U. S. COMMISSIONER 
OF FISHERIES FOR 1919 




Bureau of Fisheries Document No. 881 



PRICE, 5 CENTS 

Sold only by the Superintendent of Documents, Government Printing Office 

Washington, D. C. 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1920 



t5.- or -? 



6^ 






4 

CO 



-^ 



CONTENTS. 



Page. 

Introduction 5 

Bass, chironomid, and algal relations 6 

Importance of algal mats as forage 8 

Field characters of various algal mats 8 

Bosmina and Yolvox association 9 

Scapholeberis and Mougeotia association 10 

Daphnia and Aphanizomenon association 11 

Mayflies in the food of bass 13 

The direct function of plants in fishponds 13 

Summary 14 

Tables 14 

Bibliography 19 

3 



SOME PLANTS OF IMPORTANCE IN PONDFISH 

CULTURE. 



By Emmelixe Moore, Ph. D. 



Contribution fronf the U. S. Fisheries Biological Station, Fairport, Iowa. 



INTRODUCTION. 

It is a matter of importance in the production of pondfish to con- 
trol the growth of aquatic vegetation. This can not profitably be 
done until it is known what plants enter directly into the fish dietary 
or contribute indirectly to the support of the various animal forms 
upon which fish feed. 

There is little precise knowledge of the natural food of the ad- 
vanced fry and young fingerlings of our ponds and streams. Nearly 
all of the examinations of the food content of fishes refer to the ad- 
vanced fingerling stages or to adults. The importance from an 
economic standpoint of securing information about the natural 
forage of very young fish is seen at once. So far as we know, only 
a small percentage of the fry reach maturity, and by more or less 
vague explanations the failure has been referable to our lack of 
knowledge of the food relations in their environment. 

This investigation, conducted at the U. S. Fisheries Biological 
Laboratory, Fairport, Iowa, refers primarily to the aquatic vegeta- 
tion in the food of fish which are reared in ponds and considers the 
problem from the following standpoints: What plants contribute 
directly to the food of the advanced fry and fingerlings? What 
plants contribute indirectly to their food by providing forage for the 
various animal forms upon which fish feed? The investigation 
covers the period of the summer months during two seasons, June 
20 to August 31, 1917 and 1918. 

The data presented illustrate the dependence of the young fish on 
food, mostly animals, which in turn feed on plants. The determina- 
tion of these plants, which are the basic source of the food supply 
in the ponds, forms the chief contribution of this paper. Numerous 
examinations have been made of the food content of young fish, in 
which the direct use of plants by them is revealed. The results have 
been formulated into tables (p. 14) which supplement the data al- 
ready at hand in the researches of Forbes (1880), Pearse (1918), 
Reighard (1915), and others, and indicate plant values among the 
flowering plants, the filamentous algae, and various microscopic 
plants. 

The method pursued has been to study the plant population and, 
correlatively, the contents of the digestive tract in various species of 

5 



6 PLANTS IN PONDFISH CULTURE. 

young fish. An inventory (Table 1) was taken of the plant popula- 
tion in certain poncls,« covering all forms, the larger rooted aquatics, 
the floating forms, including the filamentous algse, and the plankton. 
Simultaneously with the inventory an examination was made of the 
food found in the digestive tracts of the young fish taken from the 
ponds at regular intervals. By this means it has been possible not 
only to identify the food but to determine the character of the forage 
grounds of the fish and to consider the various plants and the animal 
associations of importance in the economy of the pond. 

Collections of fish were made at weekly intervals and, if not ex- 
amined at once in their fresh condition, were kept in an alcohol- 
formalin preserving fluid until needed. In examining the food the 
method of Pearse (1918) was employed, that is, the food content of 
the digestive tract was pressed out upon a glass slide, moistened, 
and examined under the dissecting and compound microscopes. All 
figures in the tables referring to food content represent volumetric 
percentage estimates. Measurements in lengths are given in milli- 
meters and exclude the caudal fin. 

A brief and general description of the ponds under investigation 
will assist in making the interpretation. The accompanying map 
from an earlier publication of the Bureau shows clearly the position 
and arrangement of the ponds at the Fairport station. They are 
grouped in six series, A, B, C, D, E, and F, respectively, the ponds 
in each series being numbered independently. The investigations 
here recorded were concerned only with series B and D, the former 
composed of six small, the latter of nine somewhat larger dirt ponds. 
The areas of the specific ponds studied, that is, 16B and 1,2,3,8, and 
9D, vary from 0.22 to 0.85 acre. Water is supplied to each 
through inlet pipes connected with a large reservoir, which in turn 
is supplied from the Mississippi Eiver. The depth varies from 
about 6 inches near the inlet pipes to 7 or 8 feet at the outlet. Plants 
common to the ponds of the region have been introduced; marsh 
plants such as cat-tails, Sagittaria, Bidens, and Eleocharis occupy 
the shallower portions; sedges bind the borders of the deeper por- 
tions; and floating and rooted aquatics flourish within the pond 
area. Various aquatic insects and other animal forms have found 
their way into the ponds, and practically natural conditions prevail. 

BASS, CHIRONOMID, AND ALGAL RELATIONS. 

It is shown in Table 2 that the chironomid larvae are among the 
most important single items of food taken by the young of the 
largemouth black bass during the summer. The larvae of a certain 
species of the chironomids removed from the digestive tract were 
identifiable and later checked up with specimens taken from the ponds. 
These proved to be Orthocladius nivoriundus Fitch., a species com- 
mon in the ponds and the one upon which the bass chiefly fed. The 
body walls of this larva are thin and transparent, and when lightly 
crushed under a cover glass the food content can be readily deter- 
mined with the microscope. It was this identification of the alga 
in the crushed specimens taken from the bass that gave the clue 
to the chain of food relations subsequently to be described. 

" See accompanying map showing topography of the ponds under investigation. 



U. S. B. F— DOC. 881. 




1 10188"— 20. (To faco i). (J.) 



PLAiSTTS IN PONDFISH CULTURE. 7 

Previous to the identification of this chironomid in the fishponds 
the inventory of the plants had disclosed the interesting association 
of the larval stage of this insect with the alga, Mougeotia genu-fiexa. 
The alga was exceedingly abundant and produced a most remark- 
able and beautiful formation. This formation, or algal mat, as it 
may be called, was composed of delicate, light-green filaments of 
gossamer-like threads which were interwoven intricately in the form 
of loose-meshed rolls suspended near the surface of the water. The 
author's attention was attracted by a large number of elliptically- 
shaped bags, or cases, lightly held in the meshes of the algal mat. 
These proved to be the larval cases of the chironomid in question. 
While foraging for food the larvse move in and out of their cases, 
retaining their hold, meanwhile, by their caudal hooks. In feeding 
they draw toward them filaments from the loose meshes of Mou- 
geotia, or they forage directly from the outer walls of their cases, 
to which this alga is applied in the construction of the case, renew- 
ing the filaments as fast as they become depleted. The larvae con- 
tinue to feed upon this alga as long as the supply lasts, which is 
generally only until the middle of July, for by that time this species 
of alga, which flourishes during the early part of the season, has 
passed the stage when floating mats are readily formed. There- 
after it becomes scattered through the partial disintegration or break- 
ing up of the filaments. It is at this time that the characteristic 
" knees " or swellings in the cells occur which give to this form of 
Mougeotia its specific name, genufexa. It is while engaged in 
these feeding operations that the larvae fall prey to the bass. 

Several hundred larvae of Orthocladms nivoiiundus were examined 
to determine to what extent other algae contributed to their food 
supply. The determination is a simple matter. The larvae are 
lightly crushed under the cover glass by a slow, forward movement 
of the thumb, a slight pressure being sufficient to push out the con- 
tents of the digestive tube. The material is teased out under the 
microscope, and the problem becomes one of identification of the 
algae. Almost without exception larvae taken from the mats of 
Mougeotia showed a forage value of 100 per cent of this alga. From 
larvae taken at random in pond 3D, from habitats in which other 
algae were the chief constituents and Mougeotia appeared only as a 
small factor in the heterogeneous assortment, this alga again formed 
the bulk of the food. Specimens of 0. nivoriundus were hatched in 
a watch glass to which had been added a variety of algae as well as 
Mougeotia, and it is interesting to note that the young selected the 
latter invariably. It is not surprising, for Mougeotia is one of the 
most delicate of the filamentous forms and possesses a brittleness 
which apparently recommends it to the larvae, for when observed in 
their feeding operations they were seen to snap off filaments in one- 
cell and two-cell lengths with great rapidity. This preference for 
Mougeotia was observed in the very earliest stages of larval growth, 
and it continued to be shown to pupation. 

Later broods of Orthocladius nivoriundus^ of which there appeared 
to be three during the summer, found their natural forage among 
other algae which succeeded Mougeotia gemiiiiexa^ such as Mougeotin 
sphcerocarpa^ i^pirogyra nitida, S. TnajuscuJa, Q^dogonium, Hyclro- 
dictyon reticulatuni, Lyngbya, and various microscopic forms present 
in the algal mats. 



O PLAISTTS IN PONDFISH CULTURE. 

IMPORT A XCE OF ALGAL MATS AS FORAGE. 

The larva of the chironomid, Orthocladius nivoriundus, forms an 
important item in the dietary of the hirgemouth black bass. In 
turn the alga Mougeotia and other filamentous types supply forage 
for the chironomids. Thus these common pond plants contribute 
in a material way to the support of the bass. 

Nearly all of the aforementioned algse are commonly distributed 
in ponds. Where they do not occur and the region is within 
their range, they can easily be introduced into the ponds by trans- 
ferring a roll or wad of the alga before it dries out. If the alga is 
to be transferred by mail it should be rolled in a wet cloth, wrapped 
in thick paper, and dispatched at once. 

Unfortunately the notion exists that algal mats serve no useful 
purpose, and wasteful practices prevail in the seining operations. 
Without discrimination they are raked out, thrown upon the bank, 
and left to decompose, regardless of kind or function in the economy 
of the pond. The author's observations thus far on the value of 
algal mats, which may be called locally " moss," " moss blanket," or 
" water moss," lead to the conclusion that discrimination must be 
exercised if the ponds are to be properly stocked with useful forage 
plants. For help in such discrimination the species which com- 
monly produce the algal mats, or " moss," floating on the surface of 
ponds, are given as follows: Cladofhoi^a crispata^ Hydrodictyon 
reticulatvmi, Pitlwphora cedogonia var. vaiK^herioides^ (Edogonium 
Tnartenicense^ Rhizocloniuin hieroglyphlcum^ and Spirogyra species. 
Generally not one form alone produces the mat or blanket but a com- 
bination, as Cladophora and Pithophora; Hydrodictyon, (Edogo- 
nium, and Cladophora, etc. 

Blankets in which Cladophora, Pithophora, and Rhizoclonium 
are the prominent forms appear to be least desirable, though the 
subject warrants further investigation. This blanket complex re- 
produces and forms a coarse, thick mat which readily covers a pond 
and shuts out the light. Under control, however, this mat may be 
regarded as useful. It should be conserved near the edges only. 

FIELD CHARACTERS OF VARIOUS ALGAL IVIATS. 

The following field characters will assist in discriminating the 
different kinds of algal mats or blankets : 

Moiigeotia genwflexa when abundant forms a loose, filmy, floating 
aggregation of delicate, light-green, gossamerlike threads lightly 
suspended near the surface of the water and easily wafted about 
by the wind. It is as difficult to scoop up in the hand as a floating 
spider web would be. This alga does not accumulate in sufficient 
quantity to become detrimental, since its filaments are so delicate and 
form so loose a mesh that light is not appreciably shut out by it. 

Mougeotia sj>ha'rocarpa is also a delicate alga, though a little less 
so than M. genuftexa^ and its growth habit is different. It has a 
light yellow-green frothy look and floats on the surface of the water 
as a thin film. It is found in the sheltered places usually, though 
it may spread over a small pond as a surface film when undisturbed 
by the wind. The frothy appearance is due to the very active photo- 
synthetic capacity of tlie alga, the oxygen bubbles being confined. 



PLAINTS 11^ POIiJ'DriSH CULTURE. 9 

meanwhile, in the meshes of the filaments. This alga compares 
favorably with M. genuflesca as a food producer. It appears in 
abundance in the ponds later in the season than the foregoing species 
and has been observed repeatedly in the examination of the larval 
food of Orthocladius, Pseudochironomus, and Stratiomyia. 

Spirogyra species are generally a vivid green. They more often 
form a part of an algal complex, though they may occur nearly pure 
in round mats of varying size. They can be identified easily by the 
slimy, silky feel of the single threads or filaments. When held out 
of the water the single threads drip and curl up on drying. 
Spirogyra loeheri may develop in a pure stand enveloped in a mass 
of transparent jelly. 

(Edogonium marfenicense often forms the upper layer on the mat 
of Cladophora. Upon aging, it fades to a pale yellowish color and 
acquires a soft cottony feel. Chironomids are active feeders upon it. 

(E. sp"- does not form a mat but occurs as an epiphyte on the 
larger aquatics and on the coarser filamentous algse. The slender 
naias (Naias fleodlis) and the water- weed {Elodea canadensis) may 
become completely swathed in it by midsummer. It is an extremely 
small form of (Edogonium which in the aggregate takes on an olive- 
green look. It has the characteristic cottony feel. All things con- 
sidered, it doubtless affords forage to a greater number of pond 
herbivores than any other alga of the ponds. Chironomids, snails 
(Planorbis and Succinea), and the blunt-nosed minnows, as indi- 
cated by their food contents, show a preference for this alga. 

Pithophora mdogonia var. vaifcherioides consists of short filaments 
which on aging look and feel like coarse, dark hair. It is generally 
to be found with Cladophora and in the mat-forming stage occupies 
the stratum beneath it or becomes interwoven with it. 

Cladophora crhpata forms the coarsest and thickest algal mats in 
our ponds. The mats, or portions of them, have a coarse, heavy look 
and a harsh feel. When the mat is lifted out of the water it feels 
tough and gives one the impression of handling wet, coarse, brown 
paper or coarse loosely-woven cloth. 

Hydrodictyon reticulatum^ or water-net, is easily distinguished 
when floated out on the hancl by means of the characteristic four to 
five sided meshes. It may form in sufficient abundance to produce a 
heavy mat covering the surface of small ponds. 

These " rough and ready " field characters should assist the un- 
initiated in discriminating the most common and widely distributed 
representatives of the mat-forming algae of our pond waters. It is 
recognized of course that the microscope, together with keys and il- 
lustrations, is the only sure method of identification. 

BOSMINA AND VOLVOX ASSOCIATION. 

The plankton studies in pond 2D showed a conspicuous association 
of the small cladoceran, Bosmina longirostris^ and the green alga, 
Volvox, species perglohator and spermatospha^ra. The association of 
these organisms, Bosmina and Volvox, is important in terms of fish 
food. The Bosmina afford a direct means of subsistence to the young 
bass ; and the Volvox. through their contribution to the food supply of 
the Bosmina, an indirect one. 

° A valuable forage species unidentified to date but probably near howardii. 
140188°— 20 2 



10 ' PLANTS IN PONDFISH CULTUPvE. 

By reference to Table 2, it is seen that the young bass find in the 
small Bosmina a favorite natural food. It was selected by them 
from a varied and abundant zooplankton consisting of cladocerans, 
copepods, and rotifers. In the smallest fry examined the Bosmina 
content reached 100 per cent. For example, in the examination sev- 
eral specimens under the average of 12.2 mm. measured 10 mm. and 

11 mm., and in all cases, the smaller the fry taken from the environ- 
ment of Volvox, the larger the percentage of Bosmina in the food 
content, indicating that this is not only the earliest but the pre- 
ferred natural food of the young bass. 

It was found that Bosmina occupied the upper stratum of water in 
the open areas as well as the more sheltered weedy portions of the 
i:)onds. Their presence is indicated to the naked eye by the appear- 
ance, as it were, of a fine sprinkling of dust particles continually 
gyrating in the surface film of water. They occur in the greatest 
numbers just below the surface, and in this location they are accessi- 
ble to the fry as they rise to feed. 

The Volvox accumulated also in the upper stratum of water. The 
pulse of this alga coincided with that of Bosmina, but declined before 
any distinct diminution of Bosmina was noted. Further observa- 
tional studies disclosed the direct dependence of Bosmina upon Vol- 
vox for subsistence. 

Plankton catches from the upper stratum were taken repeatedly, 
and the feeding habits of Bosmina observed under the compound 
microscope. It was rarely possible to identify the food once taken 
into the digestive tract, because in most cases the mandibles grind 
the food particles beyond recognition. Occasionally, however, par- 
ticles slip by whole, and when these could be seen through the trans- 
parent body walls the animal was lightly crushed under a cover 
glass to make the identification more sure. Bits of broken coenobia 
of Volvox were identified, and these graded into the ground material 
characteristic of the digestive tract. In most cases the feeding hab- 
its were observed directly by watching the maneuvers of the living 
animal. Volvox was in the reproductive stage, and organisms with 
antherozoids, or sperms, were exceedingly abundant. The Bosmina 
in their feeding operations attached themselves to a bundle of ripe 
antherozoids, and by a rapid movement of the legs, characteristic of 
all cladocerans, winnowed the sperms within the body walls, from 
whence they were wafted into the mouth. This continued until the 
bundle of antherozoids was appreciably diminished, and the Bosmina 
whirled off to other feeding grounds, in which the constituents were 
often too small to identify as they were wafted into the body. Vol- 
vox, however, continued to remain a source of nutriment until its 
decline. 

This interdependence of the organisms, Bosmina and Volvox, was 
observed in pond ID also, but the plankton pulse was not manifested 
by so large a quantity of Bosmina in this pond. 

SCAPHOLEBERIS AND MOUGEOTIA ASSOCIATION. 

It was found that Scapholeheris mucronata^ a larger cladoceran, 
succeeded the Bosmina in the food of the older fry, and investigation 
followed to determine its food relations among the algse of the ponds. 



PLANTS IN PONDFISH CULTURE. 11 , 

Plankton catches showed a larger percentage of Scapholeberis in 
jjond ID than in all others. Attention was then concentrated upon 
this pond. Plankton studies were made from various regions in the 
pond to determine the specific plant habitat of the cladoceran. This 
proved to be the scum or film produced by the alga, Mougeotia 
sphm'ocarpa^ in the quieter portions of the pond. In these regions 
the algal complex teemed with Scapholeberis, the feeding grounds 
being conspicuously localized in the region of the Mougeotia fila- 
ments. 

The examination of the food content in the digestive tracts of 
Scapholeberis revealed a miscellaneous diet of small unicellular and 
palmelloid alga3 which abounded in the Mougeotia complex. The 
most common forms were small diatoms, and such green algae as 
Spha?rocystis. Oocystis, Caelastrum, and Schizochlamys. 

The association of this cladoceran with the Mougeotia complex 
adds another point in favor of the introduction and cultivation of 
Mougeotia to supply a natural forage in fishponds. 

The Scapholeberis pulse in pond ID attained its maximum in late 
July and early August. At that time it supplied a fair percentage 
of the food of the largemouth black bass (Table 2) and a high per- 
centage of the food of the bluegill (Table 3). 

Ponds ID and 2D have differed in the contribution they made to 
the food supply of the young fish in the matter of quantity as well 
as variety. This was particularly true of the Bosmina pulse which 
occurred in both ponds simultaneously but to a lesser degree in pond 
ID. Birge and Juday (1911) state: "The answer to the question 
of why different bodies of water differ so widely in productivity is 
wholly beyond our knowledge." In these ponds, however, a partial 
explanation may be sought in the difference in kind and quantity of 
living plants as well as in the accumulations of debris during suc- 
ceeding seasons. 

In physical features the ponds are similar. They are equally deep, 
and they are surrounded by a similar vegetation. They have been 
treated alike, that is, they have been wintered full, not dry. Such 
draining as has been necessary to conduct the seining operations has 
been temporary only. Physiologically, however, they are more or less 
distinct because of the dissimilar character of the vegetation in them. 
Pond ID has been richly stocked with floating algse which at times 
have covered the surface. Few of the larger rooted aquatics are 
present. Pond 2D has no algal mats or blankets, but fully one-tenth 
of the surface area has been covered by the lar^e-rooted aquatic, 
Potamogeton iUhioensis, interspersed in places with the nonrooted 
Ceratophyllum, or hornwort. In these ponds are present, apparently, 
the requisite conditions to produce a conspicuous plankton pulse of 
great economic value in terms of the natural forage of fish fry by 
supplying in quantity organisms which are preferred by the fry 
during the early days of feeding. 

DAPHNIA AND APHANIZOMENON ASSOCIATION. 

Data in the tables show that a high percentage of food is supplied 
by the daphnids. They are recognizecl herbivores in the ponds, and 
it remains to explain their particular plant preferences and associa- 
tions. 



12 PLANTS IN PONDFISH CULTURE. 

A remarkable illustration of sucli an association was presented dur- 
ing the present season in the studies connected with pond 9D, in 
which Daphnia pulex^ one of the largest of the claphnids, was pro- 
duced in enormous quantity by natural means. The blue-green alga.^ 
Ajyhanizomenon fos-aqmv^ contributed directly to its support and 
proved to be the most desirable food of a heavy, natural culture of 
Daplinia pulex. 

The author's first observation of this association in the pond oc- 
curred on June 21, 1918. At this time a "bloom" of the Apliani- 
zomenon was approaching its maximum. It was so abundant that 
the water appeared blue-green and oily. A few hand strokes of the 
dip net would bring up a quart of it in concentrated form. The 
individual colonies are ordinarily microscopic, but during the acceler- 
ation of growth in " bloom " production the colonies are considerably 
augmented and become readily distinguishable. They appear as 
flocculent masses, 7 to 16 mm. long and less than half as wide. 
They are delicate and tissuelike and assume the form of flattened 
spindle-shaped masses lightly suspended in the water at all depths, 
from the surface to the bottom of the pond. Practically a pure stand 
had developed, for there were few representatives of other floating 
alga3 present. The station records noted the presence of the algse in 
May. From that time until June 21, the date of the author's first 
observation, multiplication must have taken place with great rapidity, 
and it continued to do so until the maximum was reached in the 
interval of July 24 to 30, when the algae could be rolled up from the 
bottom like mush. 

This conspicuous growth of algee in the pond was attended by one 
equally remarkable in the number of Daphnia produced. The 
Daphnia swarmed among the algas, forming practically a pure cul- 
ture of Daphnia pulex. A rough estimate by volume, obtained by 
the gravity method, showed approximately 75 cc. per cubic meter. 
Accurate determinations w^ere difficult because of the accompanjdng 
algal debris in the concentrations. When the 'algal maxinunn was 
attained the Daphnia pulse had already begun to decline. Cypris, 
copepods, and rotifers increased in the zooplankton and Clathro- 
cystis, Volvox, and Pleodorina in the phytoplankton. 

The daphnids fed continuously upon the Aphanizomenon. The 
entire process of feeding could be observed easily by placing them 
in a watch glass or in a hollow glass slide and observing them with 
the compound microscope. The flocculent masses of the alga were 
wafted into the open walls of the body and fed forward toward the 
mouth by the action of the legs in the manner so aptly described by 
Birge (1918). During the feeding operations the Daphnia were 
offered a mixed plankton, but invariably they retained only the 
Aphanizomenon in the food current streaming toward the mouth. 
Observations on the feeding habits were continued from time to time 
during a period of five weeks, and it was easily seen that the abun- 
dant natural forage provided in Aphanizomenon was one of the de- 
termining factors in the high productivity of Daphnia pvlex. 

By reference to Tables 4 and 5 it is seen that Daphnia formed a 
high percentage of the food content in the orange-spotted sunfish and 
catfish with which the pond was stocked. Data are not at hand for 
the very young catfish since it was desirable not to disturb the ponds 



PLANTS IN PONDFISH CULTURE. 13 

by seining during the breeding period, but the large size of the 
fingerlings (Table 5) at the date recorded seems worthy of note and 
readily explainable in terms of an abundance of desirable natural 
food. 

The succession of causes, physical and physiological, which have 
led to the remarkable acceleration of growtKi in the alga, Aphani- 
zomenon, and the accompanying culture of daphnids is not easy to 
explain; yet it is desirable to record the method of treatment of the 
pond which has produced this extraordinary development. The pond 
covers an area of 0.66 acre and is free from floating plants. In the 
shallow portions there are submerged aquatics such as Naias AndPota- 
mogeton pusillus; and around the edge, a little of the blanket-form- 
ing alga, Glado'phora^ crispata. In general it is an open pond free 
from the larger aquatics or their accumulations. It could easily have 
become "seeded down" by spores of Aphanizomenon through inlet 
waters from the supply reservoir which in turn receives the river 
water. This alga is common in the supply waters and is distributed 
in season to the ponds. Daphnia pulex are also common in the ponds. 
A contributing cause of the great " wave " of Daphnia is possibly 
due to the fact that the pond has been wintered dry during successive 
seasons, the freezing and drying processes affecting the winter eggs 
of the daphnids beneficially. 

MAYFLIES IN THE FOOD OF BASS. 

Reference to Table 2 indicates the importance of mayfly larvae in 
the food of the young largemouth black bass. The mayflies are 
herbivores. The researches of Needham (1905), Morgan (1913), 
and Clemens (1917), on the life histories of these insects have shown 
that they subsist on a variety of plants in our lakes and streams, the 
familiar articles of diet being diatoms, unicellular and filamentous 
algse, and the larger aquatic plants, the latter generally in a partial 
state of disorganization. Unfortunately, time has not permitted in- 
vestigation of the plant associations of this group of insects in 
small ponds. From the few records of examination, however, it may 
be forecasted that an important habitat preference of some species of 
the larvfe is among the larger potamogetons. 

THE DIRECT FUNCTION OF PLANTS IN FISHPONDS. 

The tables show a forage value of plants which can not be regarded 
as merely accidental. By reference to Table 7 it becomes evident that 
the young of the buffalofish favor an admixture of animal and plant 
substance. The absence of grit in the digestive tract and the presence 
of plant materials, such as the staminate flowers of Elodea, for ex- 
ample, which are found only at or near the surface of the ponds, illus- 
trate the wide range of their feeding habits. The high percentage 
in the food content of the flagellate plants, Pandorina, Eudorina, and 
Pleoddrina, is suggestive of the value of the small things among the 
pond plants. 

The niost conspicuous function of plants in the fishpond is found 
in their indirect relations, in their contribution to the forage of 
myriads of animal forms upon which fish feed. This paper has 
emphasized this function of plants in its consideration of animal- 



14 



PLANTS IN PONDFISH CULTURE. 



plant associations, and it is through a more complete understanding 
of such associations that the method of rationing the ponds to in- 
crease their productivity by natural means can be approached. 

SUMMARY. 

1. Chironomid larvae are among the most important single items 
in the dietary of young bass. 

2. The identification of the food content and plant associations of 
the chironomids indicates the importance of cultivating certain 
algal forms in the ponds to provide adequate forage requirements. 

3. Mat-forming algae of certain types provide valuable forage 
areas for chironomids and cladocerans. 

4. The Bosmina-Volvox association is of special importance in 
providing the first forage materials for the bass fry and the young 
bluegill. 

5. The Scapholeberis-Mougeotia association is important in pro- 
viding a later food for the advanced fry stage. 

6. The Daphnia-Aphanizomenon association develops a heavy cul- 
ture of daphnia. 

7. Plants are of importance directly in supplying a high percentage 
of food to the advanced fry of the buffalofish. 

8. The blunt-nosed minnow in a pond habitat subsists mainly upon 
plants. 

9. The rationing of ponds for a continuous and abundant supply 
of natural forage must depend upon a more precise knowledge of 
the animal and plant associations. 

TABLES. 

[Note. — All flares in the tables referring to food content represent volumetric per- 
centage estimates. Measurements in lengtlis are given in millimeters and exclude the 
caudal fin.] 

Table 1. — Inventory of Aquatic Plants in Certain Ponds of Series B and D, 

Fairpobt, Iowa." 

[P means present; A means present in abundance.] 



Aquatic plants. 



June, 1917. 



Pond 
ID. 



Pond 
2D. 



Pond 
3D. 



Pond 
8D. 



Pond 
16B. 



June, 
1918. 



Pond 
9D. 



Flagellates: Euglena sanguinea 

Blue-green algae: 

Aphanizomenon flos-aquae 

Microcystis 

Clathrocystis 

Ccelosphserium 

Merismopedium 

Oscillatoria 

Lsmgbya martensiana 

Anabsena circinalis 

Anabfena flos-aquse 

Rivularia natans 

Diatoms: 

Navicula 

Synedra 

Pleurosigma 

Cocconeis 

Melosira 

Tabellaria fenestrata 

Fragilaria 

Gomphonema 

Amphora 

• a Inventory not exhaustive but sufficiently detailed to serve as a working basis. 



PLANTS IN PONDFISH CULTURE. 



15 



Table 1. — Inventory of Aquatic Plants in Certain Ponds of Series B and D, 
Fairport, Iowa — Continued. 



Aquatic plants. 


June, 1917. 


June, 
1918. 


Pond 
ID. 


Pond 
2D. 


Pond 
3D. 


Pond 
8D. 


Pond 
16B. 


Pond 
9D. 


Green algje: 

Cosmarium pyramidatum 


P 
P 




P 
P 


P 
P 


P 
P 


A 


C. undulatuni 


P 


p 


C notibile 


p 


Closterium monilif eruin 


P 




P 
P 


P 
P 
P 
P 






C. lanceolatum 




A 


A 










Staurastrum polymorphum 




P 
P 
P 
P 
P 


P 


P 
P 


p 


Selenastrum 










P 
P 
P 
A 
P 






Spirogyra communis 


P 
















S . varians 




P 
















S. nitida 


P 
A 
P 


P 
P 
P 








S. crassa 


A 
A 




P 




S. tenuissima 






S. gravilleana . . . 


P 






Mougeotia genuflexa 






A 
A 


















M. sphaerocarpa 


A 
















P 
P 
A 
P 
P 






Pandorina morum . . 




P 




A 
A 
P 
P 


p 


Pleodorina californica 






p 




P 


P 
P 


P 
P 




Volvox perglobator 


P 


Volvox spermatosphsera 










P 


P 
P 








Botrvococcus 
















P 










P 
P 
P 








Anchistrodesmus 


















P 
A 
P 




p 


Hydrodictyon reticulatum 




P 
P 
P 






Pediastrum duplex 


P 


P 


P 
P 




Ulothrix 




rRdognniiiTn riviila.r« 


A 
A 
A 
A 


A 

A 


P 




CE. sp 


A 
P 
A 
A 

A 
P 

P 




A 










Cladophora crispata . . . 


P 




P 


P 








Pithophora cedogonium var. vauche- 


A 


P 






P 


Chara 








Flowering plants: 

Tvpha latifolia ... 


P 
P 


P 
P 
A 


P 




P 










P 
P 
A 
A 
P 
A 
P 








P. pectinatus 






A 










P 
A 
P 
A 


P 




P 


A 
P 
A 
P 




A 




P 




Elodea canadensis 


P 


P 








Lemna minor 


P 


P 










A 


P 






P 


A 












P 
P 










A 

A 
P 








A 


A 



























16 



PLANTS IN PONDFISH CULTURE. 



Table 2. — Food Content of Largemouth Black Bass ( Micropterus sal- 
MoiDEs), Advanced Fey and Fingerlings, in Certain Ponds at Fairpobt, 
Iowa. 





Date. 


a 
o 


1 

a 

A 
CO 


< 


Animals. 




Cladocerans. 


.2 


5 


1 


.2 



a 
1 


a 

•73 




a 

a 

g 

P3 


o 

o-°. 

o 




-a 

a 



1 




1917. 


3D 

3D 
3D 
2D 
3D 
ID 
2D 
3D 
3D 
3D 
3D 


No. 
eZ 

2 
5 

16 
6 
5 
3 

15 
5 
4 
5 


Mm. 
20 

31 

31.5 

12.2 

33 

42.7 

31 

36.9 

41.5 

43 

43.2 
















97.3 

42 

10 

16.8 

18.3 

33.4 

16.7 

15.4 

30 

67.5 

18 




July 5 


1918. 




5 


25 

63.5 
13.3 
7.1 

"s.'s' 

26 
6 

12.5 
16 


"i" 

"ij"' 
...... 


5 

1.2 
2.5 
2 
35 

.7 

2 

10 

6 








July 11 


3.1 


1.2 




July 18 


60 


6 


0.9 


Do 




July 25 


is.'s' 


6.2 








Do" 








Do 

























































\ 




Animals— Continued. 


Plants. 








t 








« 


^ 


















ffi 


8 








a 


fl 












Date. 


•0 
> 

.2 

1 


qa 

53 


> 
>> 

1 
a 

03 


> 

a 



03 


i 

h 


1 
1 


> 

i 

'■3 


cci.2 

1 


8 



C8 



> 


a 

d 

•a 





03 

f 

.a 

4J 


1 

qa 

2 
'3 






P5 


s 


ft 


fi 


-< 


is 





t) 


> 


> 


e 


Ph 


!? 




1917. 




































2.5 














1918. 


























Tiilv ", 






20 












2.5 














5 


8 








5 
















July 18 




1.2 














1 ?l 










Do 




4.2 

16.4 


2.5 

12 


5 
19 


4.2 






56 












July 25 


5 
















Do 


26.7 










3.3 








Do 


44.3 
25 


4.8 
30 


6 








.6 
7 








1 fi 
























10 
2 




























2S 










14 








2 


8 


3 





















o Bosmina and Volvox association. 

6 Scapholeberis and Mougeotia association. 

c Chiefly Orthocladiusand Cricotopussp., Tanypus decoloratus Mall, and Pseudochironomusrichardsoni 
Mall. The identifications of chironomids were made by Dr. R. A. Mutkowski and Dr. O. A. Johannsen. 

d Mainly Dytiscid beetles. ^ . „ , 

e From H. F. Schradieck's unpublished reports. The larvae in the food content were identified as 
Orthocladius nivoriundus. The algse upon which these chironomids had fed consisted of 100 per cent 
Mougeotia genuflexa. 



PLANTS IN PONDFISH CULTURE. 



17 



Table 3. — Food Content of Bluegill (Lepomis pallidus), Advanced Fry and 

FiNGERLINGS, IN CeKTAIN PoNDS AT FaIBPORT, IoWA. 













Animals. 




Cladocerans. 








e 








Date. 






,d 




•s 






C3 


8J 
> 








^ 










. 


1 


a 


03 

a 


H 03 

c o 


i. 
11 




._• 




1 


.2 


si 






"S 




£1 


ti 




S-ia 


"s 


3 




2 


f1 


qa 
>1 






o 


P, 








"d 


C8 


t>> 




03 


eS 






P, 


CQ 


< 


m 


M " 


s 


<J 


I? 


o 


o 


o 


S 




1918. 




No. 


Mm. 




















July 25. 




2D.... 
ID.... 
2D.... 
2D.... 
ID.... 


10 
18 
25 
17 
5 


12.4 
18.9 
13.4 
15.6 
36.9 


66.9 
9.4 
43.6 
49.9 
4.5 


'i7.'2' 


11.1 

28.4 
19 

12.4 
52 


'si.'i" 

9 

12.4 
12.6 


10 

"e.i' 


"6." 6' 
.8 
.6 
4 


11 
9.2 
13.8 
15.2 
11 






Do 






Aug. 1 






Do 






Aug. 8. - 


2 


5 











Animals 


— Contd. 








Plants. 


V 


















ffi 




















Date. 


t 
1 


i 




i 


if 

c3 














a 








a 


o 

ft 
o 

3 

Ph 


<a 
"S 

•a 


•a 

t3 


S3 
03 

a 

< 


a 

o 

5 


i 
> 

> 


a 


.2 

o 

o 


03 

'S. 


3 

'3 

o 


1 

n. 

02 




1918. 




























July 25. 


















1 












Do. 


1.4 










0.3 








1.3 
.5 


0.3 
.6 


0.3 








0.6 


0.8 
3.2 
3 


0.4 


0.3 
1.4 


4.4 


o.'e' 




Do 






1.2 
3 


2.9 


Aug. 8. . 




2 








1 


























o Chiefly Tanypus decoloratus Mall and Pseudochironomus richardsoni Mall. 

Table 4. — Food Content op Orange-Spotted Sunfish (Lepomis humilis), Ad- 
vanced Fry and Fingerlings, in Pond 9D, Fairport, Iowa. 





1 

5 

P. 
03 


.a 
"& 

a 

a> 
2 
> 

< 


Animals. 


Plants. 




Cladocerans. 


3 
i 

.2 
O 


p. 

§ 

1 

a 
"3 

a 


1 


si 
> 

■V 

1 

§ 

1 


2 





t 


a 

n 

1 
a 


1 


to 

a 

1 




Date. 




s 

3 


o 

o 


3 
o 
o 

— . o 


a 


1918. 
July 15 


No. 
2 
1 
5 
12 
16 
19 
10 


Mm. 

30.5 

71 

18.6 

25.6 

22.5 

23.3 

42.5 


19.5 
10 
39 
31.9 
52 
27.1 
6 












80.5 

30 

25 

16.1 
6.5 
4.2 

57.5 














Do 










10 


.9 

'12 " 




50 
6 










July 18 


'ih'.k' 

6 
20.4 
5.1 


6 
.8 
1.5 


9 

12 

.9 
18.4 
3 


15 

19.5 
27.3 
25.6 
14.5 










July 25 










July 26 


3.1 




0.6 

4.2 
.4 


0.9 


0.6 




Aug. 2 




Aug. 8 


2 














o Daphniaand Aphanizomenon association. 



18 



PLANTS IN PONDFISH CULTURE. 



Table 5. — Food Content of Channel-Cat (Ictalurus punctatus), Finger- 
lings, IN Pond 9D, Fairport, Iowa. 











Animals. 
















■CO 




m 


> 

03 




Date. 


1 


a 


•S 


B 






— a 




■a 
■■g 






a 


^ 

S 


a- 


O 


o 




1-^3 




1 


_« 






ft 






A 


o 


^ 


2.3 0. 


Q 




<V 






CO 


■< 


fi 


o 


O 


O 


o 




^ 


m 




1918. 


No. 


Mm. 


















July 25 




2 
6 


51.5 
54.1 


37.5 

3 8 


is. 3 


20 
2 5 


2.5 

4 2 


30 

28 3 






7 5 


Aug. 2 


3 3 


2 5 


2 3 


Aug. 16 


6 


58.3 


4.2 


17.5 


5.8 


2.2 


58.3 



















Date. 


Animals— Contd. 






Plants. 








.4 

a 


^ 
A 


1. 

O 


S 

2 

o 


1 
.2 


o 

> 


t^ a 


a 

3 
Id 

-a 

8 


ID 

s 


July 25 


1918. 






12.5 
13.3 

5.8 














Aug. 2 


7.5 


15.8 






1.2 


"i.'7" 


1.66 




Aug. 16 


3.3 


0.83 


33 











Table 6.- 



-FooD Content of Blunt-nosed Minnow (Pimephales notatus) in 
Certain Ponds at Faieport, Iowa. 











.=5 


Animals. 


Plants. 




























-a 




■o 


^ 




M 










Date. 


"H 


a 

a 


1 


ft 


a . 

J3— • 


cS.'S 
3"^ 


_2 03 


1 




1 

C3 


M 






(^ 


ft 


-< 





o 


-< 


55 ^ 


a 


o 




3 




1918. 




No. 


Mm. 


















July 26. . . 




9D 
9D 
8D 


1 

2 

9 


49 

46.5 

45.1 


5 
















Aug. 7 




17.5 
4.4 


7.5 
.55 


"i'l 


47.5 

4.4 






Aug. 8 


6.7 




3.9 




Aug. 15 


8D 


4 


46.2 


1.3 


5 








27.5 


1.75 


75 















Plants— Continued. 


Date. 


3 
XI 

o 


03 

i 

"ca 

a 
'S 

o 


C3 


oS 

a 

B 

03 

a 


03 

.g 

ft 

CO 


1 
"ca 

s 


a 

3 
S 

1 

02 


ftg- 

ii 
11 

.2 o 


ft 

a 

3 

•a 
§ 


1 


1 


1918. 
July 26 












5 


5 


10 

20 
2.8 
2.5 


80 






Aug. 7 ! .. 






2.5 
6.7 








Aug. 8 1 4.4 

Aug. 1.5 1 .. 


1.1 


28.9 
55 


7.2 
5 


3.3 
1.25 




3.3 


15.5 


I 











PLANTS IN PONDFISH CULTURE. 



19 



Table 7. — Food Content of Btjffalofish (Ictiobus bubilus and I. cyprinella), 
Advanced Fry and Fingerlings, in Pond 16B, Fairport, Iowa.« 









d 


Animals. 


Plants. 












°ri 




•a 


n 








Date. 


.1 




« 


03 

•a 


1 


1 


H 


cm 


^81 


©"cS 


i 


o 






02 


> 




!fci 

5 


■a 


1 


5E 

CO 


a 




a 
5 


2 


5 




1917. 


N-n. 


Mm. 






















July 12. . 




7 
20 


12 
19.9 






5 
7 


20.2 
3.8 






1.2 
3.1 


0.6 
3.1 




5.5 


July 24 


3.1 


15.2 




1.3 


3 


Aug. 24 


15 


29.6 


6.2 


25.8 


6.8 


12.2 


0.1 




1.1 


6.4 


2 


3 2 








Date. 


Plants— Continued. 








i 


C3 


3 


i 


i 




■a 


.2^ 










a 


1 


i 


a 

3 


a 

03 


'3 


0) 

s 


T3 

1 


o 


•I a 

io 




1 






W 


> 


Ph 


w 


flH 


Ph 


m 


.« 


m 


O 


fi 




1917. 


























July 12.. 




7.1 




5.1 


15.4 


30.6 


1 




8 


0.1 




0.1 




July 24 


.1 




15 


2 


3 






4.2 


1.5 


19.8 


9 


6 


Aug. 24 




0.1 


31.3 








0.1 


2.8 


.2 


.3 


1.2 

















o Fry hatched in jars May 17 to 22, 1917, and transferred to pond May 25, 1917. 



BIBLIOGRAPHY. 
BlEGE, E. A. 

1918. The water fleas (Cladocera) : In Fresh-water biology, by H. B. 
Ward and G. C. Whipple, Ch. XXII, pp. 676-740. New York. 
BiEGE, E. A., and Juday, C. 

1911. The inland lakes of Wisconsin : The dissolved gases of the water and 
their biological significance. Wisconsin Geological and Natural 
History Survey, Bulletin No. XXII, Scientific Series No. 7, xx 
and 257 pp. Madison. 
Clemens, W. A. 

1917. An ecological study of the mayfly, Chirotenetes. University of 
Toronto Studies, Biological Series No. 17, 43 pp., 5 figs., 5 pis. 
Toronto. 



COKER, R, 
1916. 



Forbes, S 
1880. 

1883. 
Forbes, S, 
1908. 

Juday, C. 
1907. 



Moore, E. 
1915. 



station : its equipment, organiza- 
U. S. Bureau of Fisheries, Vol. 
Washington. 



E. 
The Fairport fisheries biological 

tion, and functions. Bulletin, 

XXXIV, for 1914, pp. 383-405. 
. A. 
On the food of young fishes. Bulletin, Illinois State Laboratory of 

Natural History, Vol. I, No. 3, pp. 66-79. Peoria. 
The food of the smaller fresh-water fishes. Ibid., No. 6, pp. 65-94. 
. A., and Richardson, R. E. 
The fishes of Illinois. Natural History Survey of Illinois: State 

Laboratory of Natural History, Vol. Ill, cxxxi and 3.57 pp. 

A study of Twin Lakes, Colorado, with especial consideration of the 
food of the trouts. Bulletin, U. S. Bureau of Fisheries, Vol. 
XXVI, for 1906, pp. 147-178. Washington. 

The potamogetons in relation to pond culture. Bulletin, U. S. Bureau 
of Fisheries, Vol. XXXIII, for 1913, pp. 251-292. Washington. 



20 PLANTS IN PONDFISH CULTURE. 

MoBGAN, Anna H. . 

1913. A contribution to the biology of mayflies. Annals, Entomological So- 
ciety of- America, Vol. 6, pp. 371-413, Pis. xlii-liv. Columbus. 
Needham, J. G. 

1905. The mayflies and midges : In Mayflies and midges of New York ; third 
report on aquatic insects, by J. G. Needham, Kenneth Morton, and 
O. A. Johannsen. New York State Museum Bulletin No. 86, pp. 
17-36. Albany. 
Pkahse a S 

1918. The food of the shore fishes of certain Wisconsin lakes. Bulletin, 
U. S. Bureau of Fisheries, Vol. XXXV, for 1915-1916, pp. 245-292. 
Washington. 
Reighabd, Jacob. 

1915. An ecological reconnoissance of the fishes of Douglas Lake, Cheboy- 
gan County, Michigan, in midsummer. Bulletin, U. S. Bureau of 
Fisheries, Vol. XXXIII, for 1913, pp. 215-249. Washington. 
Shiba, A. F. 

"1917. Notes on the rearing, growth, and food of the channel catfash, Icta- 
lurus punctatus. Transactions, American Fisheries Society, Vol.. 
46, No. 2, pp. 77-88. New York. 

TiTCOMB, J. W. 

1909. Aquatic plants in pond culture. U. S. Bureau of Fisheries Docu- 
ment No. 643, 31 pp. Washington. 
Waed, H. B. 

1896. A biological examination of Lake Michigan in the Traverse Bay 
region. Bulletin Michigan Fish Commission, No. 6, 71 pp. Lansing. 

o 



